n 1  :  the process whereby particles of liquids, gases, or solids intermingle as the result of their spontaneous movement caused by thermal agitation and in dissolved substances move from a region of higher to one of lower concentration  2 a  :  reflection of light by a rough reflecting surface  b  :  transmission of light through a translucent material dif*fu*sion*al adj 
 
 
 
Similar sounding terms:  de·vi·a·tion  di·vi·sion 
 
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